Double-piston internal combustion engine



May 1940- B. FlALA-FERNBRUGG 2,199,625

DOUBLE-PISTON INTERNAL coMBUs'ripn ENGINE Filed Ju 4, 1933 3Sheets-Sheet 1 Fig.1 F5 2 In ventor:

May 7, 1940. B. FlALA-FERNBRUGG DOUBLE-PISTON INTERNALOOMBUSTION ENGINEFiled June 4, 1958 5 Sheets-Sheet 2 In vent P: 514? M21 y 7, 1940- B.FlALA-FERNBRUGG 2.1 9.625

" DOUBLE-PISTON INTERNAL COMBUSTQIQN ENGINE Filed June 4, 1938 5Sheets-Sheet 3 Patented May 7, 1940 UNITED STATES DOUBLE-PISTON INTERNALCOMBUSTION ENGINE Benno Fiaia-Fernbrusl, Vienna, Germany Application.June 4, 1938, Serial No. 211,765 In Germany, formerly Austria, June 11,1937 7 Claims.

My invention relates to a double-piston internal combustion engine, thatis to say an internal combustion engine, wherein two pistons work in acommon cylinder and drive diflerent crank shafts or a common crankshaft. Hitherto, in such double-piston internal combustion engines theordinary crank drive wasemployed for taking the drive from the pistons,that is to say a crank drive, wherein the crank pins move on circularpaths.

My invention differs from the known doublepiston internal combustionengines in that for the drive of at least one of the two pistons apiston drive operating according to the cycloid system is provided,wherein the crank pin describes a 'cyclpid, for example a hypocycloid.

Where the two pistons drive a common crank shaft, the cycloid drive isconveniently employed in conjunction with the inner piston, and possiblyalso in conjunction with the outer piston.

If a separate crank shaft is provided for each piston, the cycloid crankdrive may be employed in conjunction with one of the crank shafts or inconjunction with both crank shafts.

In the case of a multi-cylinder engine with aligned cylinders, thecycloid crank drives may be alternately employed for driving one and theother of the crank shafts, for a favorable distribution of the masses.

In some cases it is of advantage to construct the cycloid crank driveencased.

The cycloid system crank drive is known in itself, but hitherto it hasnot been employed in conjunction with double-piston internal combustionengines. In such engines however, its employment ofiers distincttechnical advantages, as will be explained hereinafter.

In the drawings accompany ng this specification and forming part thereoftwo embodiments of double-piston internal combustion engines accordingto my invention are illustrated diagrammatically by way of example.

In the drawings:

Figs. 1 and 2 show a double-piston internal combustion engine, whereineach piston actuates a separate crank shaft, the figures being sectionsin planes perpendicular to one another.

Figs. 3 to 5 are similar representations of a double-piston internalcombustion engine according to my invention, wherein the pistons actuatea common crank shaft, Fig. 4 being a section in the plane IV-IV of Fig.3 and Fig. 5 a section in the plane VV of Fig. 3.

Figs. .6 and 7 indicate the paths of the crank pins and of the pistonsof the engines shown in Figs. 1 and 2 and Figs. 3 to 5 respectively.

' In all Figures 1 to 5, l is the cylinder, in which the upper piston 2and the lower piston ii move. The mixture is drawn in through suctionslots 4 and the combustion gases are expelled through exhaust slots 5.The mixture is ignited by means In the embodimentshown in Figs. 1 and 2each piston actuates a separate crank shaft I and 8 respectively. Thecrank shafts are interconnected by means of gears 9 to II of a suitableratio, for example 1 to 2, the intermediate gear l0 rotating about anaxle' l0 (Fig. 2) fast on the casing l2, while the other two gears arekeyed to their associated crank shafts. The crank shafts themselves aresuitably mounted in a rotatable manner in the casing I2- In theembodiment shown in Figs. 1 and 2 each of the pistons 2 and 3 isconnected to the associated crank shaft through a hypocycloid crankdrive. For this purpose each of the' crank pins I3 and ll of the crankshafts I and 8 carries loosely a sleeve l5 and I6 respectively, each ofwhich carries a gear l1 and i8 respectively and an eccentric l9 and 20respectively, the gear I! and eccentric IS on the one hand and the gearl8 and the eccentric 20 on the other hand being rigidly interconnected.The gears l1 and I8 roll on the fixed internally toothed annuli 2| and22 respectively. The connecting rods 23 and 24 of the pistons 3 and 2embrace with their big ends 25 and 26 the eccentrics l9 and 20respectively.

The operation of this arrangement is as follows: The combustible mixtureis drawn into the cylinder through the suction slots 4, ignited with theaid of the sparking plug 6 and the combustion gases are expelled fromthe cylinder through the exhaust slots 5. The reciprocatory movement ofthe pistons 2 and 3 is transmitted through the hypocycloid crank driveto the crank shafts l and 8. During the clockwise rotation of the crankshaft 1 the gear I! rotatably mounted on the crank pin. I3 rolls on theannulus 2|,

so that the centre of the associated eccentric l9, which is rigidlyconnected to the gear' II, describes the cycloid 01 illustrated in'Fig.6. The associated piston 3 describes at uniform rotational speed of thecrank shaft 1 the time-distance diagram K1 shown in Fig. 6. C2 and K2are the corresponding diagrams for the upper eccentric 20 and the upperpiston 2. \w

In the embodiment shown in Figs. 1 and 2 the two pistons are connectedtotheir'crank shafts through respective hypocycloid crank drives, but itis possible, without deviating from the spirit of my invention, tosubstitute one of these crank drives by an ordinary crank drive,.whereinthe crank pin describes a circle. An embodiment of this nature is shownin Figs. 3 to 5 in conjunction with an engine, wherein both pistons actupon a common crank shaft 1. In this embodiment only the lower piston 3is connected to the; crank shaft I through a hypocycloid drive, whichcomprises, as the embodiment previously described, an eccentric l9, 9.gear I'l rigidly connected thereto and an internally toothed annulus 2I. But the gears l1 and 2| are not in direct engagement, they areinterconnected through change speed gears 21 and 28, which are fast withone another, the gear 21 being an internally toothed annulus and meshingwith the gear l1 and the gear 28 meshing with the annulus 2|. The gears21 and 28 are loosely rotatable about a crank element 29, which connectsthe crank shaft 1 to the crank pin l3, on which the gear I! and theeccentric 19 are freely rotatable. The upper piston 2 is connected tothe crank shaft 1 through an ordinary circular crank drive of infiniteconnecting rod length, comprising links-30 engaging a slide 32, in whicha crank pin 3| of the shaft 1 reciprocates with the aid of a cross slide33. In such a crank drive the higher harmonics do not arise.

The ratio between the gears I1 and 21 and 28 and 2| respectively ispreferably such that the total ratio is 1 to 3.

The operation of the engine according to Figs. 3 to 5 is in principlesimilar to that of the engine shown' in Figs. 1 and 2. The centre of theeccentric l9 describes the cycloid C1 shown in Fig. '7 and the piston 3connected to the eccentric l9 describes the time-distance curve K1 alsoshown in Fig. '7. The centre of the crank .pin 3| describes the circle kshown in Fig. 7 and the timedistance curve of the piston 2-is indicatedin this figure at K2.

The connection of the outer piston 2 to the crank shaft I. might also beeffected with the aid of two cranks and two connecting rods of finiteconnecting rod length.

Figs. 6 and '7 show that as regards the lower piston 3, there are fourpiston strokes of different lengths at each complete revolution of theassociated crank shaft, (see time-distance diagrams K1 for the piston3). Consequently, the double piston engine according to my invention hasa characteristic which is substantially different from that of the knowndouble-piston engines. The

time-distance diagrams of the piston of a doublepiston engine accordingto my invention present the picture of a two-stroke engine withpractically complete expulsion of the combustion gases withoutscavenging pump and with inner cooling of the cylinder by an expansionstroke.

Further, in the double-piston engines according to my invention thesuction volume is smaller than the working expansion volume, so that theoperating pressures are well utilized, which is particularly importantin the case of compression engines. Moreover, the engine according to myinvention requires no control elements and the working pistons pass bythe suction and exhaust slots, which are so disposed that the engine canoperate according to the continuous fiow principle.

The engine according to my invention may be constructed as acarburetter, Diesel or semiin the direction of rotation of the crankshaft or in the opposite direction, that is to say if the angles a and 5(Fig. 6) through which the cycloid lines of symmetry deviate from thecylinder axis are variable, the compression ratio of the doublepistonengine may be altered during running or while stationary, for example itmay be increased or decreased. If the engine and the device for turningand fixing the annuli are suitably constructed, the engine may bechanged over to reverse rotation by turning the annuli about their axesopposite the direction of rotation of the engine, i. e. by altering thesign of a or p.

I wish it to be understood that I do not desire to be limited to theexact details of construction shown and described for obviousmodifications will occur to a person skilled in the art.

In the claims appended to this specification no selection of anyparticular modification of the invention is intended to the exclusion ofother modifications thereof and the right to subsequently make claim toany modification not covered by these claims is expressly reserved.

I claim:

1. In an internal combustion engine, the combination of a crank shaft, acylinder, opposing pistons in said cylinder having a combustionchamber'between them, a driving means between said pistons and saidcrank shaft comprising a cycloid drive for one of said pistons adaptedto' reverse the direction of movement of said piston in said cylinder atleast four times for each rotation of said crank shaft so as to givefour piston strokes of said piston for each such crank shaft rotation.

2. An internal combustion engine as set forth in claim 1 in which thecycloid drive is hypocycloid and is set with relation to the crankshaftto give unequal piston strokes of its corresponding piston.

3. An internal combustion engine as set forth in claim 1 in which thecycloid drive includes a generating gear and an annulus and a changespeed gearing disposed between the generating gear and: the annulus.

4. In an internal combustion engine, the combination of a crank shaft, acylinder, opposing pistons in said cylinder having a combustion chamberbetween them, a driving means between said pistons and said crank shaftcomprising a cycloid drive for each of said pistons, said drives beingadapted to give two stages of approach of said cylinders toward eachother for each rotation of the said crank shaft.

5. An internal combustion engine as set forth in claim 4 in which thedriving means between the pistons and the crank shaft are hypocycloidcrank drives.

6. In an internal combustion engine, the combination of a crank shaft,2. cylinder, opposing pistons in said cylinder having a combustionchamber between them, a driving means between said pistons and saidcrank shaft comprising a cycloid crank drive for an inner pistonadjacent said crank shaft and a circular crank drive for the other outerpiston at greater distance from said crank shaft.

7. An internal combustion engine as set forth in claim 6 in which saiddriving means between the pistons and the crank shaft embody aconnecting rod of infinite length employing a crank loop around thecrank shaft having a transverse sliding movement relative to said crankshaft.

